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Immunity, Infection and Evolution

Study charts hotspots for bat virus

Edinburgh scientists have helped pinpoint world regions most at risk of bat viruses spilling over into humans.

West Africa, sub-Saharan Africa and South East Asia are most at risk from bat viruses leading to new emerging diseases in people, according to the new global map.

The map, led by researchers at UCL with the Zoological Society of London (ZSL) and the University of Edinburgh, shows risk levels caused by a variety of factors.

These include large numbers of different bat viruses found locally, increasing population pressure, and hunting bats for bush meat.

Disease carriers

Approximately 60-75% of reported human emerging infectious diseases (EIDs) are zoonotic, in which infectious diseases in animals are naturally transmitted to humans.

Bats were chosen as the focus of the study, as they are known to carry multiple zoonotic viruses and are the suspected origin of rabies, Ebola and SARS (severe acute respiratory syndrome). Scientists identified the factors contributing to the transmission of zoonotic diseases, enabling risk maps to be created for each.

For example, mapping for potential human-bat contact, they found sub-Saharan Africa to be a hotspot, whereas for diversity of bat viruses, South America was found to be most at risk.

By combining the separate maps, researchers created the first global picture of the overall risks of bat viruses infecting humans in different regions.

Virus outbreak

The research, using data published between 1900 and 2013, identified West Africa as the highest risk hotspot for zoonotic bat viruses.

This area was outside the endemic range proposed by previous studies but has since experienced the largest scale outbreak of Ebola virus seen to date.

Transmission triggers

Published in the American Naturalist, the study identified factors that are important for driving the early stage of virus transmission from bats to humans.

These factors influence specific points in the process, which starts with the presence of viruses in the environment and the host organism, progressing to bats and humans coming into contact, and ending with infection of humans.

Information on the viruses carried by bats was collated by scientists at Western Michigan University and EcoHealth Alliance, who analysed more than 110 years' worth of data.
The information spanned 33 zoonotic bat viruses across 148 bat species from 453 literature sources.

These results were then modelled by researchers at UCL and ZSL to find patterns and drivers for bat-human virus sharing and map the findings onto cells across the globe to identify areas at risk.

We are seeing risk hotspots for emerging diseases where there are large and increasing populations of both humans and their livestock. As a result, settlements and industries are expanding into wild areas such as forests and this is increasing contact between people and bats.